Select Tournament mode and win a Singles match with a "C" or better rank. You will then get challenged by Duke. Defeat Duke to unlock him as a playable character. To easily play against him, set the options to 1 set and 1 game, and the difficulty to Easy. Play a Singles match and do very good by getting A's and B's to get a challenge from Duke.

Play as King

Select Tournament mode and win a Singles match with a "D" or worse rank. You will then get challenged by King. Defeat King to unlock him as a playable character. To easily play against him, set the options to 1 set and 1 game, and the difficulty to Easy. Play a Singles match and do very bad by getting C's and E's to get a challenge from King.

Frying Pan racket

Get three strikes in a row in the Pin Crusher mini-game to unlock the Frying Pan racket.

Guitar racket

Defeat Duke or King in a SPT final to unlock the Guitar racket.

Tambourine racket

Make a total of 100 lob shots to unlock the Tambourine racket.

Wooden racket

Win King Of Players mode to unlock the Wooden racket.

Quick Volley skill increase

In Career mode, play the "Defend The Prize" mini-game repeatedly. Choose one prize and stand in front of it (ignore the others). Simply defend that one prize to easily win the mini-game every time and be able to increase your Volley skill as quickly as desired.